Microorganisms, Cell Structures, and Infectious Disease Fundamentals

What is a microorganism? What are the major groups of microorganisms?

: An organism too small to see with the naked eye

What are the 3 domains of living organisms and which contain microorganisms?

: Bacteria, Archaea, and Eukaryea. Bacteria and Achaea contain microorganisms

How do you write an organism name using correct binomial nomenclature?

: Genus + species and italicized

How does a microscope work? What microbes can you not see with a light microscope?

: You cannot see viruses or prions under a microscope

What is the Germ Theory of Disease? Who proved this theory?

: Germ Theory of Disease states that many diseases are caused by microorganisms (pathogens) that invade the body, grow, and reproduce. It was developed and proven in the 19th century by Louis Pasteur and Robert Koch

How do cellular stains work? Why do you need to stain microbial cells?

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Understand differences between prokaryotic and eukaryotic cell structure. What cellular structures are required for the function of microorganisms? What structures are optional and are not found in all microorganisms?

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What is the microbial cell wall made of? How is this structure different between Gram + and Gram - cells?

: Peptidoglycan a rigid structure, Gram + have thick layers, Gram - have thin layers and an outer membrane

What are the possible energy and carbon sources for microorganisms? What nutritional and environmental factors influence bacterial growth?

: Microorganisms can obtain energy from light (phototrophs) or chemicals (chemotrophs), and carbon from organic compounds (heterotrophs) or carbon dioxide (autotrophs). Their growth is influenced by nutritional factors (availability of macronutrients, micronutrients, growth factors) and environmental conditions (temperature, pH, oxygen, osmotic pressure, etc.)

What is a virus? What are the basic parts of a virus? What is needed to grow a virus in culture?

: A virus is a non-cellular infectious agent made of genetic material (DNA or RNA) enclosed in a protein coat. It cannot reproduce on its own and must infect a living host cell to replicate. The basic parts of a virus are the nucleic acid genome, the capsid (protein shell), and sometimes an envelope. To grow a virus in culture, you need living host cells

What is the difference between an animal virus, bacteriophage and plant virus? How do the life cycles vary between these types of viruses?

: Animal viruses infect animal cells, often entering by fusion or endocytosis. Bacteriophages infect bacteria, injecting their DNA/RNA through the bacterial cell wall. Plant viruses infect plant cells, usually entering through wounds or via insect vectors. Their life cycles differ mainly in how they enter host cells and how they exit, but all rely on host machinery for replication.

What are the steps in a lytic virus life cycle? What are the steps of a lysogenic virus life cycle?

: The lytic cycle is a rapid, destructive replication process where the virus immediately hijacks the host cell and causes its death. Attachment (Adsorption) Penetration (Entry) Biosynthesis (Replication & Transcription/Translation) Assembly (Maturation) Release (Lysis). Host cell bursts (lysis), releasing many new viruses to infect other cells.

What do the terms metabolism, catabolism and anabolism mean?

: Metabolism = all reactions. Catabolism = breaking down, energy-releasing. Anabolism = building up, energy-consuming.

What is ATP? Why do all living cells need ATP? Where is the energy stored in ATP?

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What is the purpose of aerobic respiration? What happens in aerobic respiration in a microorganism?

: The purpose of aerobic respiration is to generate large amounts of ATP (energy) by completely oxidizing organic molecules (like glucose) using oxygen as the final electron acceptor. In microorganisms, aerobic respiration involves glycolysis, the citric acid cycle, and the electron transport chain, resulting in efficient energy production and release of carbon dioxide and water.

What is the difference between aerobic and anaerobic respiration? How is fermentation different?

: Aerobic respiration = most efficient, oxygen required. Anaerobic respiration = less efficient, uses alternative electron acceptors like inorganic compounds. Fermentation = least efficient, relies only on glycolysis, produces organic byproducts.

What does an enzyme do? What is it made of? Why are enzymes important parts of metabolism?

: Enzymes are protein catalysts that make metabolism possible by speeding up and controlling chemical reactions.

What are anaerobic chemoorganotrophs? (Know your terminology)

: Anaerobic chemoorganotrophs are microorganisms that obtain energy by oxidizing organic compounds without oxygen.

What is the difference between sterilization and disinfection? What do you need to consider when choosing a method of microbial control?

: Sterilization is complete microbial destruction. Disinfection reduces microbial load but may leave spores or resistant organisms. Choosing a method depends on the microbe type, material, safety, cost, and required level of control.

What is pasteurization? Is this a form of sterilization?

: Pasteurization is a process of mild heat treatment designed to reduce the number of microorganisms in food and beverages. It is not sterilization

What are the hardest microbes to kill? Why? How does cell structure affect microbial control?

: The hardest microbes to kill are those with special protective structures like spores and protein capsids. Cell structure directly determines resistance to heat, chemicals, and radiation — which is why sterilization methods must be carefully chosen depending on the target organism.

How do we use antimicrobial drugs to target microbes? Which targets are best? Why?

: Antimicrobial drugs target reproduction prevention or kill the bacteria by targeting cell walls or synthesis.

These are the best targets because they maximize effectiveness while minimizing harm to the patient.

What is antimicrobial drug resistance and how does it develop? What are the 5 mechanisms microbes can use for antimicrobial drug resistance?

: Antimicrobial drug resistance is when microbes evolve the ability to survive drugs designed to kill them. It develops through genetic changes (mutations or acquiring resistance genes) and selective pressure from drug use. The five main mechanisms microbes use are: (1) drug inactivation, (2) target modification, (3) reduced permeability, (4) pumps, and (5) metabolic pathway changes

What is important about the first line of defense?

: The first line of defense is crucial because it represents the body's initial barrier against infection. It's part of the innate immune system and works to stop pathogens before they can enter deeper tissues or cause harm.

What are the 4 components of the second line of defense, and what do they do?

: Phagocytic Cells (engulf pathogens), Inflammation (localized response), Fever (systemic temperature increase), Antimicrobial Substances (chemicals that attack microbes)

What are B cells? Where do they develop? What do they do? What cell types can be made from them?

: B cells are bone marrow-derived lymphocytes that recognize antigens, produce antibodies, and generate immune memory. They differentiate into plasma cells (short-term defenders) and memory B cells (long-term protection).

What do Helper T cells do (what is their effector function)? How are they activated? Why are they important?

: Helper T cells are the regulators of the immune system. They are activated by antigen-presenting cells and then orchestrate the activity of B cells, cytotoxic T cells, and macrophages. Without them, the immune system loses its coordination and effectiveness.

What do Cytotoxic T cells do (what is their effector function)? How are they activated? Why are they important?

: Cytotoxic T cells kill the invading and dangerous cells They are activated by antigen presentation on MHC I and helper T cell signals, then eliminate infected or abnormal cells

How can microbes interact with your body? How do microbes escape from the immune system?

: Commensalism (coexistence), Mutualism (beneficial), Pathogenesis (disease causing), Opportunism. Pathogens escape through variation, hiding, biofilms, immune suppression, mimicry, and enzyme production.

What is the difference between infection and disease? What has to happen in order to have an infection?

: Infection = microbes present and multiplying. Disease = infection that causes harm and symptoms. To have an infection, microbes must enter, attach, multiply, and evade defenses.

What are normal flora and why are they important? How are they affected by antimicrobial drugs?

: Normal flora are beneficial microbes that protect, nourish, and regulate your body. Antimicrobial drugs can disrupt them, sometimes leading to harmful imbalances

What are the 4 types of hypersensitivities? Know what happens in each and what cell types are responsible.

: Type 1: Immediate IgE-mediated. Type 2: Cytotoxic. Type 3: Complex mediated. Type 4: Delayed type, cell mediated.

What is a vaccine? What are the different types? Which are better?

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What is epidemiology? Why do we study epidemiology?

: Epidemiology is the science that helps us understand how diseases spread, who they affect, and how we can control them

What are the stages of clinical infection and what happens in each?

: Clinical infection progresses through five stages: incubation, prodromal, illness, decline, and convalescence.

What are the major types of respiratory system infections? How can you acquire these? How can you spread them? What are the differences between the upper and lower respiratory systems?

: Upper respiratory infections are common and usually mild (like colds). Lower respiratory infections are more serious (like pneumonia or TB) because they affect the lungs and gas exchange. Both are acquired mainly through inhalation of droplets, close contact, or contaminated surfaces, and spread through coughing, sneezing, and touching.

Why do skin infections often present with similar symptoms? Why is it not enough to say someone has a rash? Why do you need to specify if the rash is diffuse or localized?

: Skin infections often look similar because the skin has limited ways to respond to injury or microbes. But saying "rash" alone is not enough — you need details about the cause, pattern, and associated symptoms to guide proper diagnosis and treatment. You have to specify due to treatment being different for diffused or localized.

What are the different types of wounds? Why are most wound infections caused by your normal flora? Why can these be so dangerous in the broad sense of the term?

: Wounds vary in type, but all break the protective skin barrier. Most infections come from your own normal flora, which are opportunistic once they reach deeper tissues. These infections can be dangerous because they may spread locally, invade the bloodstream, and even cause life-threatening sepsis.

What organs are included in your digestive tract? How do oxygen levels vary in different parts of your digestive tract? How do oxygen requirements affect the types of organisms that can grow in these locations?

: The digestive tract includes the mouth, esophagus, stomach, intestines, and anus. Oxygen levels decrease as you move down the tract, shaping which microbes can survive: aerobes dominate the upper tract, facultative anaerobes thrive in transitional areas, and obligate anaerobes flourish in the colon.

How can many genitourinary tract infections be prevented? How many of them cannot be permanently "cured" (you have them for life)?

: Many genitourinary tract infections (like urinary tract infections and sexually transmitted infections) can be prevented through good hygiene, safe sexual practices, hydration, and regular medical care. Some remain in the body for life, though treatments can manage symptoms and reduce transmission.

Why can meningitis be caused by so many different organisms? How do prions cause nervous system infections? How does rabies affect the nervous system?

: Meningitis can be caused by many organisms because bacteria, viruses, fungi, and parasites can all inflame the meninges. Prions cause nervous system infections by misfolding normal brain proteins, leading to progressive neurodegeneration. Rabies affects the nervous system by traveling along nerves to the brain, causing severe inflammation, behavioral changes, paralysis, and ultimately death if untreated.

Understand the interactions and composition of the blood and lymphatic system. Why are blood infections so hard to treat? How can they affect multiple organs?

: Blood infections are hard to treat because they spread rapidly, trigger dangerous immune responses, and often involve resistant microbes. Once pathogens are in the bloodstream, they can reach any organ, leading to widespread damage, multi-organ failure, and life-threatening sepsis.

What are the key characteristics of HIV? What cell types does it target? Does your immune system react against it? When do you develop AIDS? What is AIDS? What do most HIV/AIDS patients die from?

: HIV is a retrovirus that targets CD4⁺ T cells, crippling immune coordination. The immune system fights back but cannot eliminate it. AIDS develops when CD4⁺ counts fall critically low or opportunistic infections appear. Most patients die from secondary infections or cancers, not HIV itself.